Atomic layer etch process using plasma in conjunction with a rapid thermal activation process

ABSTRACT

A process for etching a film layer on a semiconductor wafer is disclosed. The process is particularly well suited to etching carbon containing layers, such as hardmask layers, photoresist layers, and other low dielectric films. In accordance with the present disclosure, a reactive species generated from a plasma is contacted with a surface of the film layer. Simultaneously, the substrate or semiconductor wafer is subjected to rapid thermal heating cycles that increase the temperature past the activation temperature of the reaction in a controlled manner.

RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/582,896, filed on May 1, 2017, which is based on and claimspriority to U.S. Provisional Patent application Ser. No. 62/434,036,filed on Dec. 14, 2016, which is incorporated herein by reference.

The present application is based on and claims priority to U.S.Provisional Patent application Ser. No. 62/434,036, filed on Dec. 14,2016, which is incorporated herein by reference.

BACKGROUND

Plasma processing is widely used in the semiconductor industry fordeposition, etching, resist removal, and related processing ofsemiconductor wafers and other substrates. Plasma sources (e.g.,microwave. ECR, inductive, etc.) are often used for plasma processing toproduce high density plasma and reactive species for processingsubstrates.

One type of process carried out in the past using plasma is atomic layeretching. Atomic layer etching is a technique to perform critical etchingwith very fine precision for semiconductor device manufacturing. Atomiclayer etching is performed on a thin layer while attempting to avoidundue sub-surface damage or undesirable modifications. Atomic layeretching may be performed to etch a very thin layer that overlays anothercritical layer. Atomic layer etching may also be employed at the end ofan etch process for removing minor amounts of a remaining layer that waspreviously etched without damaging the underlying structures. It isdesired to use atomic layer etching to have self-surface limited processreaction so uniformity is controlled by surface exposure only, notcontrolled by plasma uniformity anymore so the etch amount uniformitycan be further improved.

In the past, atomic layer etching methods included first a surfacereactive species attachment step followed by plasma ion bombardment toremove the reactive surface layer. Such ion bombardment control is onlyone aspect of the possible approach for the atomic layer etching.Traditional atomic layer etching has been very successful on filmscontaining silicon, such as Si, Si₃N₄ or SiO₂. The above traditionalmethod using ion bombardment activation, however, has not beensuccessful on other layers, particularly layers containing carbon andother low dielectric films. These other materials, for instance, areless reactive to the ion bombardment and more to the chemical reaction.Further, in some embodiments, higher temperatures are needed in orderfor the etching process to occur which can result in very long etchingcycles that provide little control over the process.

Consequently, a need exists for an etch method for etching carboncontaining films and other similar films including films having a lowdielectric constant. More particularly, a need exists for a method andprocess for performing an atomic layer etching process on the abovematerials.

SUMMARY

In general, the present disclosure is directed to a process andapparatus for carrying out a precision controlled etch on a layer,particularly on a layer contained on a semiconductor wafer. Inaccordance with the present disclosure, the process includes exposing alayer to a reactive species. The reactive species, for instance, can begenerated by a plasma source. With the possible screening grid betweenthe plasma source and the substrate, mostly reactive neutral will reachthe substrate surface without ion bombardment. While the layer isexposed to the reactive species, the temperature of the layer isincreased by exposing the layer to rapid thermal cycles. The rapidthermal cycles, for instance, can be produced by one or more pulsatinglamps. The rapid thermal cycles are capable of incrementally increasingthe temperature of the layer above the activation temperature needed forthe reactive species to react with the layer. By carefully controllingthe temperature increase in combination with the temperature increaseduration, a controlled, precision etch is carried out as the reactivespecies reacts with the layer.

For example, in one embodiment, the present disclosure is directed to aprocess for etching a layer on a semiconductor wafer. The processincludes the steps of placing a semiconductor wafer in a processingchamber. The semiconductor wafer includes a film layer. The film layer,for instances, may contain carbon. For instance, the film layer maycomprise a low dielectric film, a photoresist layer, a hardmask layer,or the like. A plasma is generated from an etchant gas. The plasmacontains a reactive species. In accordance with the present disclosure,the film layer is contacted with the reactive species. In oneembodiment, for instance, the plasma is generated in a plasma chamberand filtered through a filter structure prior to contacting the filmlayer. The filter structure includes openings that allow the reactivespecies to pass but filter out at least 65%, such as at least 80%, suchas at least 90%, of charged species contained within the plasma. Thereactive species, for instance, can comprise neutral particles.

As the film layer is being contacted with the reactive species, thesemiconductor wafer is exposed to a rapid thermal cycle. The rapidthermal cycle heats the film layer above an activation temperaturesufficient to cause the reactive species to etch the film layer. In oneembodiment, for instance, the temperature of the film layer isincrementally increased by exposing the semiconductor wafer to multiplerapid thermal cycles. Each rapid thermal cycle can be the same length oftime or can have different lengths of time. In one embodiment, the oneor more rapid thermal cycles can be produced by one or more lamps, suchas flash lamps. By exposing the semiconductor wafer to multiple rapidthermal cycles, the film layer can be incrementally etched in acontrolled manner. For instance, in one embodiment, the processcomprises an atomic layer etch process.

The temperature to which the film layer is heated, the concentration ofthe reactive species within the chamber, the duration of the thermalcycles, and the other parameters can be adjusted based upon theparticular application and the desired result. In one embodiment, forinstance, the film layer can be heated to a temperature of greater thanabout 80° C., such as greater than about 90° C., such as greater thanabout 100° C. For instance, the semiconductor wafer and/or the filmlayer can be heated to a temperature of from about 100° C. to about 300°C. during the process. The etchant gas can comprise a single gas or amixture of gases. The etchant gas, for instance, can comprise molecularoxygen, molecular nitrogen, argon, molecular hydrogen, water, hydrogenperoxide, carbon dioxide, sulfur dioxide, methane, carbonyl sulfide,trifluoromethane, tetrafluoromethane, or mixtures thereof. During theprocess, the etch rate can be carefully controlled. For instance, theetch rate can be from about 100 Angstroms per minute to about 5000Angstroms per minute.

Other features and aspects of the present disclosure are discussed ingreater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed discussion of embodiments directed to one of ordinary skill inthe art are set forth in the specification, which makes reference to theappended figures, in which:

FIG. 1 is a cross sectional view of one embodiment of a processingsystem that may be used in order to carry out the process of the presentdisclosure and includes a plasma reactor, a processing chamber, and aplurality of heating lamps;

FIG. 2 is a graph illustrating one embodiment of the cumulative etchamount that may occur during the process of the present disclosure;

FIG. 3 is a graph illustrating one embodiment of a temperature profilethat may occur during the present disclosure; and

FIG. 4 is a graph illustrating one embodiment of the relationshipbetween temperature and etch rate when a layer is exposed to a reactivespecies.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments, one or moreexamples of which are illustrated in the drawings. Each example isprovided by way of explanation of the embodiments, not limitation of thepresent disclosure. In fact, it will be apparent to those skilled in theart that various modifications and variations can be made to theembodiments without departing from the scope or spirit of the presentdisclosure. For instance, features illustrated or described as part ofone embodiment can be used with another embodiment to yield a stillfurther embodiment. Thus, it is intended that aspects of the presentdisclosure cover such modifications and variations.

The present disclosure is generally directed to a process for etchingthe surface of a substrate, such as a semiconductor wafer. The presentdisclosure is also directed to an apparatus and system for carrying outthe process. In accordance with the present disclosure, the surface of asubstrate is contacted with the reactive species while being subjectedto rapid thermal cycles. The rapid thermal cycles incrementally increasethe temperature of the surface past an activation temperature at whichthe reactive species reacts with the surface and etches the surfaceremoving a surface layer.

The process of the present disclosure is particularly well suited foratomic layer etching of certain substrates. For instance, the process ofthe present disclosure is particularly well suited to etching filmscontaining carbon.

Atomic layer etching refers to an etching process in which a surface isetched by removal of individual atomic layers. Traditionally, atomiclayer etching is a two-step process in which the surface of a substrateis reacted with a chemical component. After the reaction, the surface issubjected to plasma ion bombardment to remove the reacted surface layer.The above method, however, is not well suited to etching filmscontaining carbon and other low dielectric constant materials. Suchmaterials are less reactive to ion bombardment. In this regard, thepresent disclosure is directed to an alternative atomic layer etchingmethod using thermal activation through thermal pulsing for precisionetch amount control. Not only is the process of the present disclosurewell suited to etching various materials, including carbon containinglayers, but also can be carefully controlled in accordance with stricttolerances. By using short thermal pulsing, for instance, the reactionand etching can be stopped at each thermal pulsing cycle so the etchedamount can be controlled to a very fine resolution.

The process of the present disclosure offers various advantages andbenefits. For instance, by precisely controlling the etch amount ofvarious different layers, improvements can be obtained in the underlyingdevice being formed. For example, carbon containing films can be used innumerous and diverse applications and can be incorporated into asemiconductor device as a very thin layer which ultimately producesbetter electrical performance.

In accordance with the present disclosure, a wafer is placed in aprocessing chamber and subjected to a reactive species that can begenerated from a plasma while also being exposed to one or more thermalcycles. In one embodiment, a downstream inductively coupled plasma (ICP)source can be utilized. However, the mask removal process of the presentdisclosure also contemplates other plasma technologies such as microwavedownstream strip technology or parallel plate/inductively coupled plasmaetch technologies. Inductive plasma sources are often used for plasmaprocessing to produce high density plasma and reactive species forprocessing semiconductor substrates. For instance, inductive plasmasources can easily produce high density plasma using standard 13.56 MHzand lower frequency power generators.

Although in some embodiments, the substrate or semiconductor wafer canbe directly exposed to a plasma, in one embodiment of the presentdisclosure, a plasma is produced downstream and filtered prior tocontacting the substrate. In this regard, the plasma can be formedremotely from the processing chamber. After the plasma is formed, thedesired particles or reactive species are channeled to the semiconductorsubstrate. For example, in one embodiment, a filter structure or gridcan be used that is transparent to neutral particles that form thereactive species and not transparent to the plasma. Such processes canrequire high RF power, such as up to about 6000 watts, and in some casesrelatively high gas flows and pressure. For instance, the gas flow ratecan be about 20,000 standard cubic centimeters per minute and thepressure can be up to about 5,000 milliTorr.

Referring to FIG. 1, one embodiment of a processing chamber 110 that maybe used in accordance with the present disclosure is shown. Theprocessing chamber 110 is in communication with a plasma reactor 100. Inthe embodiment illustrated, the processing chamber 110 is designed tohold a single semiconductor wafer. In other embodiments, however, aprocessing chamber can be used that can accommodate and process morethan one wafer at a time. The processing chamber 110 is designed toaccommodate a semiconductor wafer having a suitable diameter. Thediameter of the wafer, for instance, can be from about 100 mm to about500 mm in one embodiment. For example, the semiconductor wafer can havea diameter of 200 mm, a diameter of 300 mm, or a diameter of 450 mm.Fluid flow rates into and out of the processing chamber 110 can varydepending upon the size of the substrate being processed and whethermore than one substrate is being processed at a time.

In the system illustrated in FIG. 1, the plasma reactor 100 includes aplasma chamber 120 that is separate from the processing chamber 110. Theprocessing chamber 110 includes a substrate holder 112 operable to holda substrate 114. An inductive plasma is generated in plasma chamber 120(i.e., plasma generation region) and desired particles are thenchanneled from the plasma chamber 120 to the surface of substrate 114through holes provided in a filter structure such as a grid 116 thatseparates the plasma chamber 120 from the processing chamber 110 (i.e.,downstream region). The plasma chamber 120 includes a dielectric sidewall 122 and a ceiling 124. The dielectric side wall 122 and ceiling 124define a plasma chamber interior 125. Dielectric side wall 122 can beformed from any dielectric material, such as quartz. An induction coil130 is disposed adjacent the dielectric side wall 122 about the plasmachamber 120. The induction coil 130 is coupled to an RF power generator134 through a suitable matching network 132. Reactant and carrier gasescan be provided to the chamber interior from gas supply 150 and annulargas distribution channel 151. When the induction coil 130 is energizedwith RF power from the RF power generator 134, a substantially inductiveplasma is induced in the plasma chamber 120.

In a particular embodiment, the plasma reactor 100 can include anoptional faraday shield 128 to reduce capacitive coupling of theinduction coil 130 to the plasma. To increase efficiency, the plasmareactor 100 can optionally include a gas injection insert 140 disposedin the chamber interior 125. The gas injection insert 140 can beremovably inserted into the chamber interior 125 or can be a fixed partof the plasma chamber 120. In some embodiments, the gas injection insertcan define a gas injection channel proximate the side wall of the plasmachamber. The gas injection channel can feed the process gas into thechamber interior proximate the induction coil and into an active regiondefined by the gas injection insert and side wall. The active regionprovides a confined region within the plasma chamber interior for activeheating of electrons. The narrow gas injection channel prevents plasmaspreading from the chamber interior into the gas channel. The gasinjection insert forces the process gas to be passed through the activeregion where electrons are actively heated.

The plasma generated in the plasma chamber 120, as described above, ispassed through the filter structure of grid 116 and into the processingchamber 110. The grid 116 includes openings that allow the reactivespecies to pass but filter out the charged species. The reactivespecies, for instance, can comprise neutral particles. The top surfaceof the semiconductor wafer 114 is exposed to the reactive species whichreacts and removes the surface of a film layer on the semiconductorsubstrate when the temperature of the film layer is above an activationtemperature for the reaction.

In general, the grid 116 filters out at least about 65% of the chargedspecies contained within the generated plasma. For instance, the filterstructure or grid 116 can be configured to filter out at least about70%, such as at least about 75%, such as at least about 80%, such as atleast about 85%, such as at least about 90%, such as at least about 95%of the charged species contained within the plasma. In one particularembodiment, greater than about 98% of the charged species are filteredfrom the plasma so that the film layer on top of the semiconductor waferis only contacted with the reactive species, such as the neutralparticles.

As the film layer on the semiconductor wafer 114 is contacted with thereactive species, the semiconductor wafer is also exposed to one or morerapid thermal cycles. The rapid thermal cycles incrementally increasethe temperature of the film layer to above the activation temperature ofthe reaction with the film layer and the reactive species. In general,any suitable heating device can be used to expose the semiconductorwafer to rapid thermal cycles. In the embodiment illustrated in FIG. 1,for instance, at least one lamp, such as a plurality of lamps 160 areused to heat the semiconductor wafer 114. Lamps 160 may comprise, forinstance, flash lamps. The lamps, for instance, can be incandescentlamps, such as Tungsten-halogen lamps, arc lamps, or the like. The lightsources 160 can be in operative association with a reflector or a set ofreflectors for directing light energy being emitted by the lampsuniformly onto the wafer 114. In one embodiment, for instance, the lamps160 may be designed to produce a uniform radiance distribution over asurface of the wafer.

The lamps can have any suitable configuration. In one embodiment, forinstance, the lamps can include an axis that is parallel with orperpendicular to the semiconductor wafer 114. For instance, the lamps160 may comprise a plurality of elongated lamps or can comprise aplurality of linear lamps.

In the embodiment illustrated in FIG. 1, the lamps 160 are placed belowthe semiconductor wafer 114. It should be understood, however, that thelight sources may also be placed on the side of the chamber or can beplaced above the chamber so that light directly contacts the thin filmlayer being treated. In other embodiments, lamps can be placed bothabove and below the wafer, below the wafer and on the side of the wafer,above the wafer and on the side of the wafer, or can be placed below thewafer, above the wafer, and on the side of the wafer.

The use of light sources to produce rapid thermal cycles is generallypreferred. For instance, lamps or light sources have much higher heatingand cooling rates than other heating devices. Lamps create a rapidthermal processing system that provide instantaneous energy, typicallyrequiring a very short and well controlled start-up period. The flow ofenergy from the lamps can also be abruptly stopped at any time. Thelamps can be equipped with gradual power controls and can be connectedto a controller that automatically adjusts the amount of light energybeing emitted by the lamps based upon temperature measurements of thewafer.

The temperature of the wafer during processing, can be monitored usingany suitable temperature measurement device. In one embodiment, forinstance, the temperature of the wafer can be determined usingpyrometers that measure the temperature of the wafer without contactingthe wafer.

For instance, the system of the present disclosure can include aplurality of optical fibers or light pipes which are, in turn, incommunication with a plurality of light detectors. The amount of sensedradiation is then communicated to the light detectors which generate ausable voltage signal for determining the temperature of the wafer whichcan be calculated based, in part, on Planck's Law.

In general, the system can contain one or a plurality of pyrometers.When containing a plurality of pyrometers, each pyrometer can measurethe temperature of the wafer at a different location. Knowing thetemperature of the wafer at different locations can then be used tocontrol the amount of heat being applied to the wafer. For example, inone embodiment, the system can include a controller, such as amicroprocessor. The controller can receive voltage signals from thelight detectors that represent the radiation amounts being sampled atthe various locations. Based on the signals received, the controller canbe configured to calculate the temperature of the wafer at the differentlocations. The controller can also be in communication with the lightenergy sources 160. In this manner, the controller can determine thetemperature of the wafer, and, based on this information, control theamount of thermal energy being emitted by the lamps 160. Consequently,instantaneous adjustments can be made regarding the conditions withinthe thermal processing chamber. Alternatively, instead of a close loopsystem as described above, the controller may operate on an open loopsystem. For instance, the controller can be calibrated using thetemperature sensing devices and then preprogrammed to operate the lightsources based on predicted results.

As shown in FIG. 1, the light energy sources 160 can be isolated fromthe thermal processing chamber 110 by a spectral filter or a window 162.The spectral filter 162 serves to isolate the lamps 160 from thesemiconductor wafer 114 and prevent contamination of the chamber.Spectral filter 162 is designed to allow thermal energy from the lampsto pass through and into the chamber for heating the semiconductor wafer114. In one embodiment, the spectral filter 162 may filter out light ata certain wavelength, such as the wavelength at which the pyrometersoperate in order to prevent interference. The spectral filter 162, forinstance, can be made from quartz or other similar material.

As described above, the semiconductor wafer 114 is placed on a substrateholder 112. In one embodiment, the substrate holder 112 can be adaptedto rotate the wafer during processing. Rotating the wafer promotesgreater temperature uniformity over the surface of the wafer andpromotes enhanced contact between the wafer and the reactive speciesintroduced into the chamber. In other embodiments, however, thesemiconductor wafer 114 may remain stationary during processing.

The system illustrated in FIG. 1 further includes an outlet 164. Outlet164 is for allowing gases to flow through the chamber and exit thechamber. In one embodiment, for instance, the reactive species that doesnot react with the surface of the wafer can flow into the thermalprocessing chamber 110 and exit through the outlet 164. After an etchprocess is completed, in one embodiment, any inert gas can be fedthrough the chamber and out through the outlet 164 in order to removeall reactive species from within the processing chamber.

In conducting a controlled etch process in accordance with the presentdisclosure, a plasma is first generated in the plasma chamber 120 froman etchant gas to produce a reactive species. The etchant gas maycomprise a single gas or may comprise a mixture of gases. Thecomposition of the etchant gas, for instance, can depend upon numerousvariables. For instance, selection of the etchant gas can depend upon afilm layer contained on a semiconductor wafer 114 to be etched, the etchconditions, and the amount of material to be etched off the surface ofthe wafer. Gases that may be used to formulate the etchant gas include,for instance, an oxygen source, a hydrogen source, a halogen source, andthe like. Particular gases that may be used include molecular oxygen,molecular nitrogen, argon, molecular hydrogen, water, hydrogen peroxide,carbon dioxide, sulfur dioxide, methane, carbonyl sulfide,trifluoromethane, tetrafluoromethane, and the like, or mixtures thereof.

In one embodiment, for instance, the etchant gas may comprise an oxygencontaining gas alone or in combination with an inert gas, such asnitrogen. For instance, in one particular embodiment, the etchant gasmay comprise a combination of molecular oxygen and molecular nitrogen.

In an alternative embodiment, the etchant gas may comprise a combinationof an oxygen containing gas, a halogen containing gas, and a reducinggas. The oxygen containing gas, for instance, may comprise molecularoxygen, carbon dioxide, carbon monoxide, nitric oxide, or combinationsthereof. The halogen containing gas, for instance, can contain fluorinesuch as tetrafluoromethane. The reducing gas, on the other hand, cancontain hydrogen and may comprise molecular hydrogen, ammonia, methane,or the like. An inert gas may also be present, such as molecularnitrogen, or a noble gas such as argon or helium.

The gas flow rate can vary widely depending upon the particularapplication. For instance, each gas can have a flow rate of from about50 sccm to about 20,000 sccm, such as from about 500 sccm to about10,000 sccm.

The etch process of the present disclosure can also be carried out atvarying power and pressure levels. The RF source power, for instance,can range from about 300 watts to about 6,000 watts, such as from about1,000 watts to about 5,500 watts, such as from about 3,000 watts toabout 5,000 watts. The source power can be adjusted up or down based onthe surface area of the semiconductor wafer to be treated. The pressurewithin the processing chamber, on the other hand, can also varydepending upon various different factors. The pressure for instance, canrange from about 1 mTorr to about 4,000 mTorr, such as from about 250m/Torr to about 1,500 mTorr, such as from about 400 m/Torr to about 600m/Torr.

Each of the above different parameters can be controlled in order tocontrol the etch rate during processing of the film layer on thesemiconductor wafer. The etch rate is also carefully controlled bycontrolling the temperature increase through the rapid thermal cycles.More particularly, the etch rate can depend upon the thin film beingprocessed, the etchant gas composition, the gas flow rates, thetemperature of the film layer, the pressure within the chamber, inaddition to various other factors. In general, the etch rate can begreater than about 100 angstroms per minute, such as greater than about200 angstroms per minute, such as greater than about 300 angstroms perminute, such as greater than about 400 angstroms per minute, such asgreater than about 500 angstroms per minute, such as greater than about600 angstroms per minute, such as greater than about 700 angstroms perminute, such as greater than about 800 angstroms per minute, such asgreater than about 900 angstroms per minute, such as greater than about1,000 angstroms per minute, such as greater than about 1,200 angstromsper minute, such as greater than about 1,400 angstroms per minute, suchas greater than about 1,600 angstroms per minute, such as greater thanabout 1,800 angstroms per minute, such as greater than about 2,000angstroms per minute. The etch rate is generally less than about 70,000angstroms per minute, such as less than about 50,000 angstroms perminute, such as less than about 40,000 angstroms per minute, such asless than about 30,000 angstroms per minute, such as less than about20,000 angstroms per minute, such as less than about 10,000 angstromsper minute, such as less than about 9,000 angstroms per minute, such asless than about 8,000 angstroms per minute, such as less than about7,000 angstroms per minute, such as less than about 6,000 angstroms perminute, such as less than about 5,000 angstroms per minute, such as lessthan about 4,000 angstroms per minute, such as less than about 3,000angstroms per minute, such as less than about 2,000 angstroms perminute, such as less than about 1,000 angstroms per minute.

In general, any suitable film layer can be etched in accordance with thepresent disclosure. Film layers while suited for use in the presentdisclosure, for instance, include film layers than when exposed to areactive species, such as a reactive species produced by a plasma (i.e.neutral particles), have a activation temperature of generally greaterthan about 30° C., such as greater than about 40° C., such as greaterthan about 50° C., such as greater than about 60° C., such as greaterthan about 70° C., such as greater than about 80° C., such as greaterthan about 90° C., such as greater than about 100° C. Such film layersinclude film layers containing carbon. For example, in one embodiment,the film layer being etched in accordance with the present disclosurecomprises an amorphous carbon layer. The amorphous carbon layer, forinstance, can be doped with boron.

In other embodiments, the carbon containing layer can comprise aphotoresist layer.

The process of the present disclosure is also well suited to etchingfilm layers having a low dielectric constant.

For purposes of explanation, for instance, included as FIG. 4 is a graphillustrating etch rate versus temperature when exposed to an etching gasfor a carbon containing film, such as a photoresist layer. For instance,FIG. 4 can represent an embodiment where a photoresist layer containingcarbon is subjected to an etch process in the presence of a reactivespecies produced from molecular oxygen and molecular nitrogen plasma. Asshown, etching does not occur until the temperature of the film layerreaches generally greater than about 80° C., even in the presence ofoxygen reaction reticles. In accordance with the present disclosure,rapid thermal heating cycles are used in order to incrementally increasethe temperature of the film layer and the wafer in a manner forcontrolling the etch rate during the process.

Referring to FIG. 3, for instance, one embodiment of a temperaturecontrol profile that may be used during an etch process of the presentdisclosure is shown. Referring to FIG. 3, for instance, the temperatureof the film layer increases at area 200. Area 200 represents bulkheating of the wafer and the film layer. The activation temperature ofthe reaction between the film layer and the reactive species occurs attemperature 202 on the graph. In accordance with the present disclosure,rapid thermal cycles are then used to increase the temperature from theactivation temperature 202 to a maximum temperature 204. Using rapidthermal cycles, the temperature of the film layer can be increased tothe maximum temperature 204 and then immediately reduced back down tothe activation temperature 202. For instance, each temperature cycle cancomprise a pulse of the light energy sources. Each pulse can beextremely short in order to control a reactive removal amount during theetch process. For instance, each thermal pulsing cycle of lamps can beless than about 10 seconds, such as less than about 7 seconds, such asless than about 5 seconds, such as less than about 3 seconds, such asless than about 1 second, such as less than about 800 milliseconds, suchas less than about 600 milliseconds, such as even less than about 400milliseconds. Each pulse is generally greater than about 50milliseconds, such as greater than about 100 milliseconds. After thecontrolled etch is completed, as shown in FIG. 3, the temperature of thefilm layer decreases back to an ambient.

Thus, the temperature versus time profile shown in FIG. 3 illustrateshow the film layer can be heated to the activation temperature and thenrapidly heated to a maximum temperature by flash heating causing a rapidfast temperature ramp increase. After reaching the maximum temperature,the film layer can be rapidly cooled by thermal conduction to bulk. Inthis manner, an atomic layer etching process can be carried out.

FIG. 2, illustrates the cumulative etch amount through each thermalpulsing cycle. By using short thermal pulsing, the etch amount can begradually increased and the reaction can be stopped at the end of eachthermal pulsing cycle so the etched amount can be controlled to a veryfine resolution. As shown in FIG. 2, for instance, each thermal cycleincreases the amount of material etched according curvilinear amountcreating an increasing but overall nonlinear etch rate.

While the present subject matter has been described in detail withrespect to specific example embodiments thereof, it will be appreciatedthat those skilled in the art, upon attaining an understanding of theforegoing may readily produce alterations to, variations of, andequivalents to such embodiments. Accordingly, the scope of the presentdisclosure is by way of example rather than by way of limitation, andthe subject disclosure does not preclude inclusion of suchmodifications, variations and/or additions to the present subject matteras would be readily apparent to one of ordinary skill in the art.

What is claimed is:
 1. A plasma reactor for processing one or moresemiconductor wafers, the plasma reactor comprising: a processingchamber; a plasma chamber, the plasma chamber comprising a dielectricsidewall and a ceiling, the plasma chamber disposed on a first side ofthe processing chamber, an induction coil disposed adjacent to thedielectric sidewall of the plasma chamber; an RF power generator coupledthe induction coil through a matching network, the RF power generatoroperable to energize the induction coil with RF power to generate asubstantially inductive plasma in the plasma chamber; a gas supplyoperable to provide a gas into the plasma chamber; a substrate holderdisposed within the processing chamber; a plurality of lamps configuredon a second and opposite side of the first side of the processingchamber; a window disposed between the plurality of lamps and thesubstrate holder; and a controller configured to control the pluralityof lamps to implement a plurality of thermal heating cycles to heat afilm layer on a wafer above an activation temperature, wherein theplurality of thermal heating cycles produces an overall nonlinear etchrate such that each of the plurality of thermal heating cycles increasesan etch amount on the film layer in a curvilinear manner.
 2. The plasmareactor of claim 1, comprising a separation grid separating theprocessing chamber from the plasma chamber, the separation grid operableto filter charged species generated in the substantially inductiveplasma.
 3. The plasma reactor of claim 1, further comprising a Faradayshield disposed between the induction coil and the dielectric sidewall.4. The plasma reactor of claim 1, wherein the substrate holder isoperable to rotate the wafer.
 5. The plasma reactor of claim 1, whereinthe dielectric sidewall comprises quartz.
 6. The plasma reactor of claim1, wherein the window comprises a spectral filter.
 7. The plasma reactorof claim 1, wherein the plurality of lamps comprises a plurality oflinear lamps.
 8. The plasma reactor of claim 1, further comprising a gasinjection insert disposed in the plasma chamber.
 9. The plasma reactorof claim 1, wherein the controller is configured to control theplurality of lamps to implement the plurality of thermal heating cyclesduring an etch process.
 10. The plasma reactor of claim 9, wherein thecontroller is configured to control the plurality of lamps toincrementally increase a temperature of the film layer on the wafer tocontrol the etch rate during the etch process.
 11. The plasma reactor ofclaim 9, wherein the controller is configured to adjust an amount oflight provided by the plurality of lamps based at least in part on oneor more temperature measurements of the wafer.
 12. The plasma reactor ofclaim 9, wherein each of the plurality of thermal heating cycles is lessthan about 1 second.
 13. The plasma reactor of claim 10, wherein theetch rate is an increasing and nonlinear etch rate during the etchprocess.
 14. The plasma reactor of claim 10, wherein the film layer is adoped amorphous carbon layer.
 15. The plasma reactor of claim 14,wherein the doped amorphous carbon layer is doped with boron.
 16. Aplasma reactor for processing one or more semiconductor wafers, theplasma reactor comprising: a processing chamber; a plasma chamber, theplasma chamber comprising a dielectric sidewall and a ceiling, theplasma chamber disposed on a first side of the processing chamber, aninduction coil disposed adjacent to the dielectric sidewall of theplasma chamber; a Faraday shield disposed between the induction coil andthe dielectric sidewall; an RF power generator coupled the inductioncoil through a matching network, the RE power generator operable toenergize the induction coil with RF power to generate a substantiallyinductive plasma in the plasma chamber; a gas supply operable to providea gas into the plasma chamber; a separation grid separating the plasmachamber from the processing chamber; a substrate holder disposed withinthe processing chamber; a plurality of lamps configured on a second andopposite side of the first side of the processing chamber; a windowdisposed between the plurality of lamps and the substrate holder; and acontroller configured to control the plurality of lamps to implement aplurality of thermal heating cycles to heat a film layer on a waferabove an activation temperature during an etch process, wherein theplurality of thermal heating cycles produces an overall nonlinear etchrate such that each of the plurality of thermal heating cycles increasesan etch amount of the film layer in a curvilinear manner.
 17. The plasmareactor of claim 16, wherein the controller is configured to control theplurality of lamps to incrementally increase a temperature of the filmlayer on the wafer to control the etch rate during the etch process. 18.The plasma reactor of claim 16, wherein the controller is configured toadjust an amount of light provided by the plurality of lamps based atleast in part on one or more temperature measurements of the wafer. 19.The plasma reactor of claim 16, wherein each of the plurality of thermalheating cycles is less than about 1 second.
 20. The plasma reactor ofclaim 17, wherein the etch rate is an increasing and nonlinear etch rateduring the etch process.